Polymeric Oriented Monolayers and Multilayers as Model Surfaces

Abstract

All living cells are surrounded by a lipid bilayer membrane in which a variety of proteins (e.g., enzymes) are embedded (fluid mosaic model; Figure 1). Phospholipids and cholesterol represent the major part of the lipids of a biomembrane. Figure 2 illustrates the structure of some typical amphiphilic membrane components with hydrophobic alkyl chains and hydrophilic head groups. The amount of protein in biological membranes varies between 40 and 60%(3); however, in highly specialized membranes values between 20% (myelin sheath of nerve axons; electrical isolator) and 75% (mitochondrial inner membrane; enzyme system of the respiratory chain) may occur. Furthermore, the incorporation of proteins in a membrane and in particular as reticulum on its inside (spectrin of erythrocyte mem-branes(4)) increases its stability.